1. Field of the Invention
The present invention relates to an auxiliary swivel caster wheel assembly and a caster direction-locking mechanism for a mobile utility cart, and more particularly to such a wheel assembly and locking mechanism for a mobile utility cart commonly called a “medical emergency crash cart” or simply a “crash cart”, for medical emergency use in hospitals and other medical institutions. The auxiliary swivel caster wheel assembly and direction-locking caster mechanism in accordance with the present invention provide the crash cart with improved high speed stability and maneuverability. A trigger mechanism for selectively locking and unlocking the direction-locking caster mechanism also is included.
2. Description of Related Art
A medical emergency crash cart commonly contains medical equipment, instruments, and supplies that may be required while responding to medical emergencies, particularly for medical procedures practiced in cases of cardiac emergencies. However, the crash cart may be equipped for any type of medical emergency. The crash cart generally includes a housing having a plurality of drawers, shelves, and/or compartments for storing medical equipment and supplies such as syringes and drugs. The housing is supported by a plurality of wheels or casters so that it may be moved rapidly from its place of storage to a location of a medical emergency. To provide maximum efficiency during a medical emergency, a crash cart must therefore provide both agile and stable mobility.
One drawback of many known crash carts is a lack of stability during high speed travel. First, as a crash cart must be able to maneuver quickly in small areas of patients' or hospital emergency rooms, it is desirable to support the housing on swivel casters. Second, as medical equipment, instruments, and supplies are expensive, hospitals may maintain only a limited number of crash carts (e.g. one crash cart per floor or station). Therefore, when a medical emergency occurs, a crash cart operator must rush the cart through the hospital corridors often over relatively long distances to a patient. However, the swivel casters may cause the cart to be difficult to steer at high speeds particularly when an attempt is made to change the direction of movement, for example, by going around corners in corridors or turning into a patient's room. Therefore, the crash cart operator must either reduce his speed through the corridors or risk overturning the cart. The risk of overturning increases when the operator must negotiate the cart around a corner, as swivel casters do not provide a firm pivot about which to turn but rather permit inertia of the cart to cause it to tend to continue to move in its original direction. Alternatively, a crash cart may be operated by two persons. However, this is less efficient and may, in fact, not be possible during a given emergency.
U.S. Pat. No. 4,790,610 (Welch et al.), U.S. Pat. No. 4,875,696 (Welch et al.), and U.S. Pat. No. 7,370,867 (Olson et al.) disclose mechanisms for selectively locking swivel caster wheel assemblies in predetermined positions. However, while the mechanisms disclosed in these patents have many advantages, they are not well suited for dynamic actuation while a cart is in motion. For example, actuators for these mechanisms may be located on a side of a cart and/or may be positioned for actuation by an operator's foot, or may be otherwise inconvenient for the operator to actuate while the cart is in motion.
In addition, U.S. Pat. No. 6,725,956 (Lemire) discloses a hospital bed having four wheels in contact with a floor surface, and a motorized assembly that is employed to raise and lower an auxiliary or fifth wheel away from and toward the floor. When the fifth wheel is raised, the hospital bed functions as a conventional hospital bed. When the fifth wheel is lowered, it contacts the floor surface and the motorized assembly causes the fifth wheel to rotate, which propels the hospital bed. The fifth wheel is held at a predetermined position relative to a frame of the hospital bed, thus, the fifth wheel must be raised when maneuvering the hospital bed in a small area, such as a patient's room. However, the fifth wheel cannot be raised and lowered quickly. Accordingly, the fifth wheel disclosed in the Levine Patent is not well-suited for use in emergency situations.
For these and other reasons, the crash carts and related mechanisms for improving mobility of wheeled apparatuses of the prior art are not entirely satisfactory. A need exists for an improved crash cart and related mechanisms for providing even greater high speed stability and maneuverability.